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Blast-furnace slag (BFS), which is an iron-steel factories waste occurred during the production of unrefined iron, is used as a fine aggregate or in case of being granulated, as a replacement of cement in concrete mixtures. Durability to sulfate attack, which is an important problem of structure, increased with using BFS in concrete production. ASTM C 1012 was used to determine the effect of sulfate attack and BFS replaced cement by the amount of 0, 25, 50, 75 and 100 %. For activating BFS, NaOH, NaCO3 and Na2SiO3 were used. Produced mortar cement specimens of 5x5x5 cm and 25x25x285 mm were kept in sodium sulfate solution. Length changes and strength losses were examined For examining the microstructure, specimens were cut into the size of 1 cm cubes. SEM photos were taken from the specimen surfaces and including elements were determined. Under sulfate effect, there is no ettringite form but small microcraks were seen in alkali activated BFS mortars. Porous structure was occurred in binding phases of control mortars and in this structure, needle shape ettringite crystals were formed with sulfate attack. [ABSTRACT FROM AUTHOR]

Blast-furnace slag (BFS), which is an iron-steel factories waste occurred during the production of unrefined iron, is used as a fine aggregate or in case of being granulated, as a replacement of cement in concrete mixtures. Durability to sulfate attack, which is an important problem of structure, increased with using BFS in concrete production. ASTM C 1012 was used to determine the effect of sulfate attack and BFS replaced cement by the amount of 0, 25, 50, 75 and 100 %. For activating BFS, NaOH, NaCO3 and Na2SiO3 were used. Produced mortar cement specimens of 5x5x5 cm and 25x25x285 mm were kept in sodium sulfate solution. Length changes and strength losses were examined. For examining the microstructure, specimens were cut into the size of 1 cm cubes. SEM photos were taken from the specimen surfaces and including elements were determined. Under sulfate effect, there is no ettringite form but small microcraks were seen in alkali activated BFS mortars. Porous structure was occurred in binding phases of control mortars and in this structure, needle shape ettringite crystals were formed with sulfate attack. [ABSTRACT FROM AUTHOR]